TONIGHT'S MUST-SEE

"30 Rock," 8:31 p.m., NBC. This is the year "30 Rock" seems to have it all. It has its best-comedy Emmy, the soaring popularity of Tina Fey and a pile of A-list guests. That has included Oprah Winfrey and Jennifer Aniston; now it's Steve Martin's turn. He plays a guy who invites Jack and Liz to his mansion for dinner. Soon, he has a business proposition for him and a romantic one for her. The business part is so promising that Kenneth wants to invest his savings in it. But is this guy all he claims to be?

TONIGHT'S MIGHT-SEE

"American Gangster," 8 p.m., BET. So far, this series has focused on black criminals. Now comes a switch: J. Edgar Hoover, the late FBI director, had a private war against blacks, it says. That started with his probes of Marcus Garvey and Paul Robeson, the hour says. By the 1960s, Hoover was obsessing on Martin Luther King Jr.

OF NOTE

"Ugly Betty," 7 p.m., ABC. The Young Editors Training Program could be Betty's chance to move up, but she's competing with Marc for it.

"Explorer: Lost City of the Amazon," 7 p.m., National Geographic. For four centuries, people ignored an explorer's report that there were large cities in the Amazon region. That was impossible, they said; the acidic soil prevents agriculture. Now that's being re-examined. There is evidence of 19 settlements, wide trails and an artificial soil, made from pottery and charcoal. It's an interesting report, including visits with the tribes there now.

"Grey's Anatomy," 8 p.m., ABC. When a standard surgery goes bad, Meredith, Cristina and Bailey rush in to help. Also, a sleepwalker has been seriously injured.

"CSI: Crime Scene Investigation," 8 p.m., CBS. A double murder may be linked to another case, a dozen years ago.

"ER," 9 p.m., NBC. Last week, Gates (John Stamos) decided a former soldier had been mistreated by the military. Then the guy vanished. Now Gates tries hard to find him; Sam (Linda Cardellini) feels he's trying too hard.